只会走到log的333333333这边，然后通过tolist转成list<String>形式，就不往下走了，假如去掉tolist，可以执行subscribe.
只是本人需要先将数据转成需要的List集合，再执行subscribe

mModel.getAllSearchHistoryCache().filter(new Func1<RealmResults<SearchHistoryBean>, Boolean>() {
            @Override
            public Boolean call(RealmResults<SearchHistoryBean> searchHistoryBeen) {
                Logger.e("111111111");
                return searchHistoryBeen.isLoaded();
            }
        }).flatMap(new Func1<RealmResults<SearchHistoryBean>, Observable<SearchHistoryBean>>() {
            @Override
            public Observable<SearchHistoryBean> call(RealmResults<SearchHistoryBean> searchHistoryBeen) {
                Logger.e("2222222222");
                return Observable.from(searchHistoryBeen);
            }
        }).map(new Func1<SearchHistoryBean, String>() {
            @Override
            public String call(SearchHistoryBean searchHistoryBean) {
                Logger.e("3333333333");
                return searchHistoryBean.getKeyWord();
            }
        }).toList().observeOn(AndroidSchedulers.mainThread()).subscribe(new Subscriber<List<String>>() {
            @Override
            public void onCompleted() {
                Logger.e("onCompleted");
            }
            @Override
            public void onError(Throwable e) {
                Logger.e("onError");
            }
            @Override
            public void onNext(List<String> strings) {
                Logger.e("strings:"+strings);
                mView.showSearchHistoryList(strings);
            }
        });